dax: add a facility to lookup a dax device by 'host' device name

For the current block_device based filesystem-dax path, we need a way
for it to lookup the dax_device associated with a block_device. Add a
'host' property of a dax_device that can be used for this purpose. It is
a free form string, but for a dax_device associated with a block device
it is the bdev name.

This is a stop-gap until filesystems are able to mount on a dax-inode
directly.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2017-04-19 15:14:31 -07:00
parent 7b6be8444e
commit 7205800541
4 changed files with 86 additions and 6 deletions

View file

@ -13,7 +13,7 @@
#ifndef __DAX_H__
#define __DAX_H__
struct dax_device;
struct dax_device *alloc_dax(void *private);
struct dax_device *alloc_dax(void *private, const char *host);
void put_dax(struct dax_device *dax_dev);
bool dax_alive(struct dax_device *dax_dev);
void kill_dax(struct dax_device *dax_dev);

View file

@ -645,7 +645,7 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
goto err_id;
}
dax_dev = alloc_dax(dev_dax);
dax_dev = alloc_dax(dev_dax, NULL);
if (!dax_dev)
goto err_dax;

View file

@ -30,6 +30,10 @@ static DEFINE_IDA(dax_minor_ida);
static struct kmem_cache *dax_cache __read_mostly;
static struct super_block *dax_superblock __read_mostly;
#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
static struct hlist_head dax_host_list[DAX_HASH_SIZE];
static DEFINE_SPINLOCK(dax_host_lock);
int dax_read_lock(void)
{
return srcu_read_lock(&dax_srcu);
@ -46,12 +50,15 @@ EXPORT_SYMBOL_GPL(dax_read_unlock);
* struct dax_device - anchor object for dax services
* @inode: core vfs
* @cdev: optional character interface for "device dax"
* @host: optional name for lookups where the device path is not available
* @private: dax driver private data
* @alive: !alive + rcu grace period == no new operations / mappings
*/
struct dax_device {
struct hlist_node list;
struct inode inode;
struct cdev cdev;
const char *host;
void *private;
bool alive;
};
@ -63,6 +70,11 @@ bool dax_alive(struct dax_device *dax_dev)
}
EXPORT_SYMBOL_GPL(dax_alive);
static int dax_host_hash(const char *host)
{
return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
}
/*
* Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
* that any fault handlers or operations that might have seen
@ -75,7 +87,13 @@ void kill_dax(struct dax_device *dax_dev)
return;
dax_dev->alive = false;
synchronize_srcu(&dax_srcu);
spin_lock(&dax_host_lock);
hlist_del_init(&dax_dev->list);
spin_unlock(&dax_host_lock);
dax_dev->private = NULL;
}
EXPORT_SYMBOL_GPL(kill_dax);
@ -98,6 +116,8 @@ static void dax_i_callback(struct rcu_head *head)
struct inode *inode = container_of(head, struct inode, i_rcu);
struct dax_device *dax_dev = to_dax_dev(inode);
kfree(dax_dev->host);
dax_dev->host = NULL;
ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
kmem_cache_free(dax_cache, dax_dev);
}
@ -169,26 +189,53 @@ static struct dax_device *dax_dev_get(dev_t devt)
return dax_dev;
}
struct dax_device *alloc_dax(void *private)
static void dax_add_host(struct dax_device *dax_dev, const char *host)
{
int hash;
/*
* Unconditionally init dax_dev since it's coming from a
* non-zeroed slab cache
*/
INIT_HLIST_NODE(&dax_dev->list);
dax_dev->host = host;
if (!host)
return;
hash = dax_host_hash(host);
spin_lock(&dax_host_lock);
hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
spin_unlock(&dax_host_lock);
}
struct dax_device *alloc_dax(void *private, const char *__host)
{
struct dax_device *dax_dev;
const char *host;
dev_t devt;
int minor;
host = kstrdup(__host, GFP_KERNEL);
if (__host && !host)
return NULL;
minor = ida_simple_get(&dax_minor_ida, 0, nr_dax, GFP_KERNEL);
if (minor < 0)
return NULL;
goto err_minor;
devt = MKDEV(MAJOR(dax_devt), minor);
dax_dev = dax_dev_get(devt);
if (!dax_dev)
goto err_inode;
goto err_dev;
dax_add_host(dax_dev, host);
dax_dev->private = private;
return dax_dev;
err_inode:
err_dev:
ida_simple_remove(&dax_minor_ida, minor);
err_minor:
kfree(host);
return NULL;
}
EXPORT_SYMBOL_GPL(alloc_dax);
@ -201,6 +248,38 @@ void put_dax(struct dax_device *dax_dev)
}
EXPORT_SYMBOL_GPL(put_dax);
/**
* dax_get_by_host() - temporary lookup mechanism for filesystem-dax
* @host: alternate name for the device registered by a dax driver
*/
struct dax_device *dax_get_by_host(const char *host)
{
struct dax_device *dax_dev, *found = NULL;
int hash, id;
if (!host)
return NULL;
hash = dax_host_hash(host);
id = dax_read_lock();
spin_lock(&dax_host_lock);
hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
if (!dax_alive(dax_dev)
|| strcmp(host, dax_dev->host) != 0)
continue;
if (igrab(&dax_dev->inode))
found = dax_dev;
break;
}
spin_unlock(&dax_host_lock);
dax_read_unlock(id);
return found;
}
EXPORT_SYMBOL_GPL(dax_get_by_host);
/**
* inode_dax: convert a public inode into its dax_dev
* @inode: An inode with i_cdev pointing to a dax_dev

View file

@ -10,6 +10,7 @@ struct iomap_ops;
int dax_read_lock(void);
void dax_read_unlock(int id);
struct dax_device *dax_get_by_host(const char *host);
/*
* We use lowest available bit in exceptional entry for locking, one bit for